Understanding drug dependence may require the scientific investigation of the impulsive and loss of control behavior typically exhibited by the drug-dependent. Impulsivity has been defined as the selection of a smaller more immediate reward over a larger more delayed reward. Loss of control refers to a preference for the self-controlled decision or choice, that at a later time reverses in favor of the impulsive choice. One approach to understanding both impulsivity and loss of control is by examining how delayed rewards are discounted. The discounting of delayed rewards, however, has only been rarely studied in drug-dependent individuals. In this new application, we will systematically explore the delay discounting of a variety of potential outcomes in the drug dependent and the factors that may modulate the discounting process including the discounting of health outcomes that result from AIDS-risk behavior. Two series of studies are proposed. Series One will consist of five experiments. In these experiments, we will assess delay discounting in opioid-dependent (Experiment 1), cocaine-dependent (Experiment 2), marijuana dependent (Experiment 3), alcohol-dependent (Experiment 4), and nicotine-dependent (Experiment 5) participants vs normal controls matched on age, sex, IQ, education, smoking status (for Exp 1-4), martial status, and SES. In each of these studies, we will examine the delay discounting (including sign effect and preference reversals) of (1) money, (2) primary drug of dependence, and (3) health outcomes that result from risky sexual behavior. Series Two, which is composed of four experiments, employs conditions that may modulate delay discounting. Experiment 6 and 7 will examine the effects of drug withdrawal on the delay discounting behavior of opioid- and nicotine-dependent individuals. Experiment 8 will examine the effects of alcohol administration on delay discounting in nicotine-dependent individuals. Moreover, we will use other measures of impulsivity in each study and examine the correlation of these measures with delay discounting. Collectively, these proposed measures will provide a comprehensive assessment of impulsivity in the drug- dependent. Also, we will assess AIDS-risk behavior and craving to determine whether those that engage in risky behavior, or report the drug cravings also drastically discount the future. These studies will provide systematic information about the paradoxical behavior (loss of control and impulsivity) evident in the drug-dependent, permit comparisons of these behaviors across types of drug dependence, and provide insight into the processes that may lead to engaging in AIDS-risk behavior.